The 40-year-old former Scotland international earned a stay of execution after masterminding a famous FA Cup victory over Liverpool
However, eight defeats out of nine games in League One has left the Latics hovering above the relegation zone and Dickov has decided to quit after two and a half years in the job.
Oldham statement: "After yesterday's defeat to Walsall, Paul Dickov has decided that for the good of Oldham Athletic Football Club, it is best that he steps aside."
Oldham chairman Simon Corney: "It is not down to a lack of hard work - he has been working very hard and I think the players have to shoulder a huge amount of responsibility.
"I have been at too many games now where we just haven't performed.
"When they put in a performance like they did against Liverpool, you know they have the talent and ability, and yet in the day-to-day bread and butter games, they are not showing what they need to show week in and week out.
"I feel for Paul, I really do, because he trains them hard, he works hard and does a lot of things to prepare the team, and once they cross that line, what can he do?
"It is a horrible situation. I'd like to think I will never have another manager who is a friend of mine again, because it is horrible.
"When I met with Paul for the very first time, I said to him, 'You know this can only end horribly, because either you will leave me because you are doing pretty well, or I am going to fire you', and that is the case with nearly every club.
"It is a horrible situation, but I can't let anything like that cloud my judgement because I have to do what is best for the club."